This invention relates to a braking mechanism with direction-related braking force; and more particularly to such a mechanism having advantageous use for an object such as a winding device of a recording and/or reproducing apparatus for a record-carrier tape.
A braking member having a braking surface can be applied to the circumferential braked surface of a disc which is connected to the winding device. To obtain a braking force which differs depending on the direction of rotation of the disc, the braking member is freely movable through an angle corresponding to the two directions of rotation along an arcuate pressing surface which is concentric with the disc and which is situated on a pressing element such as a pivotally mounted braking lever. The two end positions of the brake member, in which the braking lever operates with different arm lengths, are each defined by a stop comprising a stop surface. Such a braking mechanism is disclosed in DE-OS 20 49 063 to which U.S. Pat. No. 3,638,881 corresponds.
In this known braking mechanism the braking member is a brake block, whose braking surface is concentric with the circumferential surface of the disc to be braked. The braking lever has a sector-shaped slot which is concentric with the disc and in which a pin on the brake block engages, so that the brake block is freely movable along the slot in conformity with the two directions of rotation, the two ends of the slot constituting stops which define the two end positions of the brake block. If the brake block is applied to the circumferential surface of the disc by a pivotal movement of the braking lever, it will move to one of the two end positions depending on the direction of rotation of the disc and brake the disc in this position. Depending on the end position of the brake block, the braking lever operates with different arm lengths, so that depending on its direction of rotation the disc is braked with a different braking force. This direction-related difference in force is required in recording and/or reproducing appratuses because during unwinding a winding device should be braked more strongly than during take up in order to ensure that in the stationary condition the record carrier between the two winding devices remains taut.